Appendix:Mega Evolution

Mega Evolution is a transformation that only appears in certain final form Pokémon, or some Pokémon that cannot evolve. Mega-Evolved Pokémon are identified by having "Mega" in front of their name. Mega Evolution can only be achieved if there is a strong bond between a Trainer and its Pokémon.

In order to Mega Evolve, most Pokémon must be holding their appropriate Mega Stone and the Trainer must have a Key Stone. Only Rayquaza does not need a Mega Stone to Mega Evolve-- instead, it must know the move Dragon Ascent.

Introduction
In any battle, each Trainer may Mega Evolve a single Pokémon once. Mega Evolution is essentially a free action a Pokémon may make in addition to its normal move, but if a Pokémon will not use a move, it cannot Mega Evolve. Mega Evolution occurs before most actions except switching. A Mega-Evolved Pokémon will only revert back to its original state if it faints or the battle ends; if it is switched out, it will still be in its Mega Evolved state if it is switched back in.

A Pokémon cannot Mega Evolve if it is being held in the airborne phase of Sky Drop. Neither volatile nor non-volatile status conditions such as paralysis, sleep, and infatuation will have any effect over a Pokémon's ability to Mega Evolve; even if they result in the Pokémon not being able to move that turn, the Mega Evolution will occur regardless.

Mega Stones are not affected by most moves or Abilities. If they would move a Mega Stone to or from a Pokémon that could use it to Mega Evolve, the moves Bestow, Covet, Fling, Thief, Trick, and Switcheroo will fail and the Abilities Magician, Pickpocket and Symbiosis will not activate. The move Knock Off cannot remove a Mega Stone from a Pokémon that can use it to Mega Evolve, and Knock Off's power will not be increased since it cannot remove the item. The moves Embargo and Magic Room and the Ability Klutz will not prevent a Pokémon from using its respective Mega Stone to Mega Evolve.

Performing Mega Evolution will not alter the turn order, so a Pokémon with a lower Speed than their opponent will still go after them on the one turn the Mega Evolution occurs, even if their Mega Evolution increases Speed and would otherwise cause them to go first. The opposite is also true for Pokémon who lose Speed from Mega Evolution, such as Garchomp. However, turn order will be determined normally on every turn afterwards. All other stat changes and type changes of a Mega Evolution will take effect immediately and damage calculation will proceed as usual. (A Pokémon whose Mega Evolution possesses a lower Defense stat, for example, will take greater damage from Physical attacks on the turn of Mega Evolving.)

Changes in a Pokémon's Ability will also take place immediately. For example, a Sharpedo that normally has Speed Boost will not gain a boost in Speed at the end of the turn it Mega Evolves, but if it uses a biting move such as Crunch that turn, it will be boosted by Strong Jaw, its Ability as Mega Sharpedo.